package cn.gok.homework;
import java.util.Random;
import java.util.Scanner;

public class homework1 {
    public static void main(String[] args) {

        char[] yinwen = new char[]{ 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L',
                'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'};
        char[] shuzi = new char[]{'0', '1', '2', '3', '4', '5', '6', '7', '8', '9'};
        int i = new Scanner(System.in).nextInt();
        int yinwenLength = yinwen.length;
        int shuziLength = shuzi.length;
        StringBuilder sb = new StringBuilder();
        if(i%2==0){
            for (int j = 0; j < i/2; j++) {
                int r=new Random().nextInt(yinwenLength);
                int r1=new Random().nextInt(shuziLength);
                sb.append(yinwen[r]);
                sb.append(shuzi[r1]);
            }
        }else{
            for (int j = 0; j < i/2; j++) {
                int r=new Random().nextInt(yinwenLength);
                int r1=new Random().nextInt(shuziLength);
                sb.append(yinwen[r]);
                sb.append(shuzi[r1]);
            }
            int r1=new Random().nextInt(shuziLength);
            sb.append(shuzi[r1]);
        }
        System.out.println(sb);
    }

}
